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@PHDTHESIS{Zhang:809232,
author = {Zhang, Yanli},
title = {{D}evelopment of {E}mbedded {T}hermocouple {S}ensors for
{T}hermal {B}arrier {C}oatings ({TBC}s) by a {L}aser
{C}ladding {P}rocess},
volume = {312},
school = {Ruhr-Universität Bochum},
type = {Dr.},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {FZJ-2016-02521},
isbn = {978-3-95806-129-3},
series = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
Umwelt / Energy $\&$ Environment},
pages = {II, 108 S.},
year = {2016},
note = {Ruhr-Universität Bochum, Diss., 2015},
abstract = {Thermal barrier coatings (TBCs) are now being widely used
on gas turbine engines to lower the surface temperatures of
metallic substrate from extreme hot gas stream in combustor
and turbine components. The thermally grown oxide (TGO)
growth rate plays an important role in the lifetime of TBC
systems. The accurate real-time monitoring of bond-coat/
8YSZ interface temperature in thermal barrier coatings
(TBCs) in hostile environments opens large benefits to
efficient and safe operation of gas turbines. A new method
for fabricating high temperature thermocouple sensors which
can be placed close to this interface using laser cladding
technology has been developed. K-type thermocouple powders
consisting of alumel (Ni2Al2Mn1Si) and chromel (Ni10Cr) were
studied as candidate feedstock materials. A thermocouple
sensor using these materials was first produced by coaxial
continuous wave (CW) or pulsed laser cladding process onto
the standard yttria partially stabilized zirconia (7~8
$wt.\%$ YSZ) coated substrate and afterwards embedded with a
second YSZ layer deposited by the atmospheric plasma spray
(APS) process. The process parameters of the laser cladding
were optimized with respect to the degradation of the
substrate, dimensions, topography, thermosensitivity and
embeddability, respectively. Infrared cameras were used to
monitor the surface temperature of clads during this
process. The manufacture of the cladded thermocouple sensors
provides minimal intrusive features to the substrate. The
dimensions were in the range of two hundred microns in
thickness and width for CW laser cladding and less than 100
microns for pulsed laser cladding. Additionally, continuous
thermocouple sensors with reliable performance were
produced. It is possible to embed sensors manufactured by CW
laser cladding rather than by pulsed laser cladding due to
the limited bonding strength between the clads and the
substrate. Periodically droplets were formed along the clads
under improper parameters, the mechanism to this is
discussed in terms of particle size distribution after
interaction with the laser beam, melts duration and
Rayleigh’s theory. To sum up, laser cladding is a
prospective technology for manufacturing microsensors on the
surface of or even embedded into functional coatings that
can survive in operation environments for in-situ
monitoring. Production of sensors within thermal barrier
coatings (TBCs) increases the application field of the laser
cladding technique.},
cin = {IEK-1},
cid = {I:(DE-Juel1)IEK-1-20101013},
pnm = {113 - Methods and Concepts for Material Development
(POF3-113) / HITEC - Helmholtz Interdisciplinary Doctoral
Training in Energy and Climate Research (HITEC)
(HITEC-20170406)},
pid = {G:(DE-HGF)POF3-113 / G:(DE-Juel1)HITEC-20170406},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
url = {https://juser.fz-juelich.de/record/809232},
}